1. Field of the Invention
The present invention relates to a light-emitting panel and methods of fabricating the same. The present invention further relates to a micro-component for use in a light-emitting panel.
2. Description of Related Art
In a typical plasma display, a gas or mixture of gases is enclosed between orthogonally crossed and spaced conductors. The crossed conductors define a matrix of cross over points, arranged as an array of miniature picture elements (pixels), which provide light. At any given pixel, the orthogonally crossed and spaced conductors function as opposed plates of a capacitor, with the enclosed gas serving as a dielectric. When a sufficiently large voltage is applied, the gas at the pixel breaks down creating free electrons that are drawn to the positive conductor and positively charged gas ions that are drawn to the negatively charged conductor. These free electrons and positively charged gas ions collide with other gas atoms causing an avalanche effect creating still more free electrons and positively charged ions, thereby creating plasma. The voltage level at which this plasma-forming discharge occurs is called the write voltage.
Upon application of a write voltage, the gas at the pixel ionizes and emits light only briefly as free charges formed by the ionization migrate to the insulating dielectric walls of the cell where these charges produce an opposing voltage to the applied voltage and thereby eventually extinguish the discharge. Once a pixel has been written, a continuous sequence of light emissions can be produced by an alternating sustain voltage. The amplitude of the sustain waveform can be less than the amplitude of the write voltage, because the wall charges that remain from the preceding write or sustain operation produce a voltage that adds to the voltage of the succeeding sustain waveform applied in the reverse polarity to produce the ionizing voltage. Mathematically, the idea can be set out as Vs=Vwxe2x88x92Vwall, where Vs is the sustain voltage, Vw is the write voltage, and Vwall is the wall voltage. Accordingly, a previously unwritten (or erased) pixel cannot be ionized by the sustain waveform alone. An erase operation can be thought of as a write operation that proceeds only far enough to allow the previously charged cell walls to discharge; it is similar to the write operation except for timing and amplitude.
Typically, there are two different arrangements of conductors that are used to perform the write, erase, and sustain operations. The one common element throughout the arrangements is that the sustain and the address electrodes are spaced apart with the plasma-forming gas in between. Thus, at least one of the address or sustain electrodes may be located partially within the path the radiation travels, when the plasma-forming gas ionizes, as it exits the plasma display. Consequently, transparent or semi-transparent conductive materials must be used, such as indium tin oxide (ITO), so that the electrodes do not interfere with the displayed image from the plasma display. Using ITO, however, has several disadvantages, for example, ITO is expensive and adds significant cost to the manufacturing process and ultimately the final plasma display.
The first arrangement uses two orthogonally crossed conductors, one addressing conductor and one sustaining conductor. In a gas panel of this type, the sustain waveform is applied across all the addressing conductors and sustain conductors so that the gas panel maintains a previously written pattern of light emitting pixels. For a conventional write operation, a suitable write voltage pulse is added to the sustain voltage waveform so that the combination of the write pulse and the sustain pulse produces ionization. In order to write an individual pixel independently, each of the addressing and sustain conductors has an individual selection circuit. Thus, applying a sustain waveform across all the addressing and sustain conductors, but applying a write pulse across only one addressing and one sustain conductor will produce a write operation in only the one pixel at the intersection of the selected addressing and sustain conductors.
The second arrangement uses three conductors. In panels of this type, called coplanar sustaining panels, each pixel is formed at the intersection of three conductors, one addressing conductor and two parallel sustaining conductors. In this arrangement, the addressing conductor orthogonally crosses the two parallel sustaining conductors. With this type of panel, the sustain function is performed between the two parallel sustaining conductors and the addressing is done by the generation of discharges between the addressing conductor and one of the two parallel sustaining conductors.
The sustaining conductors are of two types, addressing-sustaining conductors and solely sustaining conductors. The function of the addressing-sustaining conductors is twofold: to achieve a sustaining discharge in cooperation with the solely sustaining conductors; and to fulfill an addressing role. Consequently, the addressing-sustaining conductors are individually selectable so that an addressing waveform may be applied to any one or more addressing-sustaining conductors. The solely sustaining conductors, on the other hand, are typically connected in such a way that a sustaining waveform can be simultaneously applied to all of the solely sustaining conductors so that they can be carried to the same potential in the same instant.
Numerous types of plasma panel display devices have been constructed with a variety of methods for enclosing a plasma-forming gas between sets of electrodes. In one type of plasma display panel, parallel plates of glass with wire electrodes on the surfaces thereof are spaced uniformly apart and sealed together at the outer edges with the plasma-forming gas filling the cavity formed between the parallel plates. Although widely used, this type of open display structure has various disadvantages. The sealing of the outer edges of the parallel plates, the pumping down to vacuum, the baking out under vacuum, and the introduction of the plasma-forming gas are both expensive and time-consuming processes, resulting in a costly end product. In addition, it is particularly difficult to achieve a good seal at the sites where the electrodes are fed through the ends of the parallel plates. This can result in gas leakage and a shortened product lifecycle. Another disadvantage is that individual pixels are not segregated within the parallel plates. As a result, gas ionization activity in a selected pixel during a write operation may spill over to adjacent pixels, thereby raising the undesirable prospect of possibly igniting adjacent pixels without a write pulse being applied. Even if adjacent pixels are not ignited, the ionization activity can change the turn-on and turn-off characteristics of the nearby pixels.
In another type of known plasma display, individual pixels are mechanically isolated either by forming trenches in one of the parallel plates or by adding a perforated insulating layer sandwiched between the parallel plates. These mechanically isolated pixels, however, are not completely enclosed or isolated from one another because there is a need for the free passage of the plasma-forming gas between the pixels to assure uniform gas pressure throughout the panel. While this type of display structure decreases spill over, spill over is still possible because the pixels are not in total physical isolation from one another. In addition, in this type of display panel it is difficult to properly align the electrodes and the gas chambers, which may cause pixels to misfire. As with the open display structure, it is also difficult to get a good seal at the plate edges. Furthermore, it is expensive and time consuming to pump down to vacuum, bake out under vacuum, introduce the plasma producing gas and seal the outer edges of the parallel plates.
In yet another type of known plasma display, individual pixels are also mechanically isolated between parallel plates. In this type of display, the plasma-forming gas is contained in transparent spheres formed of a closed transparent shell. Various methods have been used to contain the gas filled spheres between the parallel plates. In one method, spheres of varying sizes are tightly bunched and randomly distributed throughout a single layer, and sandwiched between the parallel plates. In a second method, spheres are embedded in a sheet of transparent dielectric material and that material is then sandwiched between the parallel plates. In a third method, a perforated sheet of electrically nonconductive material is sandwiched between the parallel plates with the gas filled spheres distributed in the perforations.
While each of the types of displays discussed above are based on different design concepts, the manufacturing approach used in their fabrication is generally the same. Conventionally, a batch fabrication process is used to manufacture these types of plasma panels. As is well known in the art, in a batch process individual component parts are fabricated separately, often in different facilities and by different manufacturers, and then brought together for final assembly where individual plasma panels are created one at a time. Batch processing has numerous shortcomings, such as, for example, the length of time necessary to produce a finished product. Long cycle times increase product cost and are undesirable for numerous additional reasons known in the art. For example, a sizeable quantity of substandard, defective, or useless fully or partially completed plasma panels may be produced during the period between detection of a defect or failure in one of the components and an effective correction of the defect or failure.
This is especially true of the first two types of displays discussed above; the first having no mechanical isolation of individual pixels, and the second with individual pixels mechanically isolated either by trenches formed in one parallel plate or by a perforated insulating layer sandwiched between two parallel plates. Due to the fact that plasma-forming gas is not isolated at the individual pixel/subpixel level, the fabrication process precludes the majority of individual component parts from being tested until the final display is assembled. Consequently, the display can only be tested after the two parallel plates are sealed together and the plasma-forming gas is filled inside the cavity between the two plates. If post production testing shows that any number of potential problems have occurred, (e.g. poor luminescence or no luminescence at specific pixels/subpixels) the entire display is discarded.
Preferred embodiments of the present invention provide a light-emitting panel that may be used as a large-area radiation source, for energy modulation, for particle detection and as a flat-panel display. Gas-plasma panels are preferred for these applications due to their unique characteristics.
In one basic form, the light-emitting panel may be used as a large area radiation source. By configuring the light-emitting panel to emit ultraviolet (UV) light, the panel has application for curing paint or other coatings, and for sterilization. With the addition of one or more phosphor coatings to convert the UV light to visible white light, the panel also has application as an illumination source.
In addition, the light-emitting panel may be used as a plasma-switched phase array by configuring the panel in at least one embodiment in a microwave transmission mode. The panel is configured in such a way that during ionization the plasma-forming gas creates a localized index of refraction change for the microwaves (although other electromagnetic wavelengths would work). The microwave beam from the panel can then be steered or directed in any desirable pattern by introducing at a localized area a phase shift and/or directing the microwaves out of a specific aperture in the panel
Additionally, the light-emitting panel may be used for particle/photon detection. In this embodiment, the light-emitting panel is subjected to a potential that is just slightly below the write voltage required for ionization. When the device is subjected to outside energy at a specific position or location in the panel, that additional energy causes the plasma-forming gas in the specific area to ionize, thereby providing a means of detecting outside energy.
Further, the light-emitting panel may be used in flat-panel displays. These displays can be manufactured very thin and lightweight, when compared to similar sized cathode ray tube (CRTs), making them ideally suited for home, office, theaters and billboards. In addition, these displays can be manufactured in large sizes and with sufficient resolution to accommodate high-definition television (HDTV). Gas-plasma panels do not suffer from electromagnetic distortions and are, therefore, suitable for applications strongly affected by magnetic fields, such as military applications, radar systems, railway stations and other underground systems.
According to a general embodiment of the present invention, a light-emitting panel is made from two substrates, wherein one of the substrates includes a plurality of sockets and wherein at least two electrodes are disposed. At least partially disposed in each socket is a micro-component, although more than one micro-component may be disposed therein. Each micro-component includes a shell at least partially filled with a gas or gas mixture capable of ionization. When a large enough voltage is applied across the micro-component the gas or gas mixture ionizes forming plasma and emitting radiation.
In one embodiment of the present invention, the micro-component is configured to emit ultra-violet (UV) light, which may be converted to visible light by at least partially coating each micro-component with phosphor. To obtain an improvement in the discharge characteristics, each micro-component may be at least partially coated with a secondary emission enhancement material.
In another embodiment, each micro-component is at least partially coated with a reflective material. An index matching material is disposed so as to be in contact with at least a portion of the reflective material. The combination of the index matching material and the reflective material permits a predetermined wavelength of light to be emitted from each micro-component at the point of contact between the index matching material and the reflective material.
Another object of the present invention is to provide a micro-component for use in a light-emitting panel. A shell at least partially filled with at least one plasma-forming gas provides the basic micro-component structure. The shell may be doped or ion implanted with a conductive material, a material that provides secondary emission enhancement, and/or a material that converts UV light to visible light. The micro-components will be made as a sphere, cylinder or any other shape. The size and shape will be determined in accordance with the desired resolution for the display panel to be assembled. Typical sizes are about hundreds of microns independent of shape.
Another preferred embodiment of the present invention is to provide a method of making a micro-component. In one embodiment, the method is part of a continuous process, where a shell is at least partially formed in the presence of at least one plasma-forming gas, such that when formed, the shell is filled with the plasma-forming gas or gas mixture.
In another embodiment, the micro-component is made by affixing a first substrate to a second substrate in the presence of at least one plasma-forming gas. In this method, either the first and/or the second substrate contains a plurality of cavities so that when the first substrate is affixed to the second substrate the plurality of cavities are filled with the plasma-forming gas or gas mixture. In a preferred embodiment, a first substrate is advanced through a first roller assembly, which includes a roller with a plurality of nodules and a roller with a plurality of depressions. Both the plurality of nodules and the plurality of depressions are in registration with each other so that when the first substrate passes through the first roller assembly, the first substrate has a plurality of cavities formed therein. A second substrate is advanced through a second roller assembly and then affixed to the first substrate in the presence of at least one gas so that when the two substrates are affixed the cavities are filled with the gas or gas mixture. In an alternate preferred embodiment, the second roller assembly includes a roller with a plurality of nodules and a roller with a plurality of depressions so that when the second substrate passes through the second roller assembly, the second substrate also has a plurality of cavities formed therein. In either of these embodiments, at least one electrode may be sandwiched between the first and second substrates prior to the substrates being affixed.
In another embodiment, at least one substrate is thermally treated in the presence of a least one plasma-forming gas so as to form shells filled with the plasma-forming gas or gas-mixture.
In a specific aspect, the micro-components, whether sphere, capillary or other shape are coated with a frequency converting coating. Phosphor is an example of such a coating. More specifically, the coating converts electromagnetic radiation generated in the plasma in the ultraviolet region of the spectrum, and converts it to the visible red, blue or green region of the spectrum.
Alternatives include putting a drop of the frequency converting material in a socket into which the micro-component is placed, or the micro-component itself can be doped with a material such as a rare earth that is a frequency converter. Examples of materials include barium fluoride or the like, yttrium aluminum garnet, or gadolinium gallium garnet. The plasma gases in the micro-component can include xenon chloride, argon chloride, etc., namely the rare gas halides.
In another aspect, the micro-components are tested as they are manufactured. The micro-components are optionally scanned for certain physical characteristics or defects, for example, in an optical field detecting shape such as sphericity and size as they drop through a tower. A micro-component displacement device can be used to remove those that are bad. At a subsequent layer, as they drop the micro-components are subjected to electron beam excitation, microwave or RF field, for example, to excite the gas. Another physical characteristic or defect is tested, such as if a certain luminous output is achieved, and if achieved, it is preliminarily accepted. Those for which a desired luminous output is not achieved are discarded, for example, through the use of a second micro-component displacement device.
In yet still another aspect, the micro-components are preconditioned by being excited for a predetermined period of time. Examples include taking the micro-components that passed the initial test, placing them in a container and exciting them, for example, for 5 to 10 hours. Alternatively, they can be placed between large parallel electrodes. After the batch run, they are dropped through a tower as they are excited, output detected and the ones that do not excite are knocked out of the stream.
Other features, advantages, and embodiments of the invention are set forth in part in the description that follows, and in part, will be obvious from this description, or may be learned from the practice of the invention.